Tire retreading equipment

ABSTRACT

A tire retreading tube for use with a tire retreading rim formed from a pair of axially-adjacent rim sections, one of said sections having a cutout for the reception of the valve stem extending from the tube body and being formed with threads adjacent the tube. The tube has an extension of generally cylindrical form through which the stem extends, so that the extension surrounds the portion of the stem adjacent the tube, and functions as a spacer element and is effective to limit movement of the stem and the tube relatively to the rim section. Suitably, the spacer element threadedly engages the stem adjacent the tube, has a body which essentially fills the cutout circumferentially, and has end flanges to overlie the adjacent faces of the rim section with which it is to be associated.

REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 942,878, filedDec. 17, 1986, now U.S. Pat. No. 4,780,949.

FIELD OF THE INVENTION

This invention relates generally to tire retreading and is moreparticularly concerned with the tube or bladder used in tire retreadingoperations and with its cooperation with the other parts of theretreading apparatus.

BACKGROUND OF THE INVENTION

Tire retreading or "recapping" is a common, widely-used procedure,particularly in the case of truck tires, to renew the tread of tireshaving a sound carcass but having their tread worn relatively thin as aresult of many miles of use. In conventional retreading operations, astandard method involves abrading the road-engaging portion of the tirecarcass to be retreaded, wrapping an un-cured rubber strip or "cushion"around it, adhesively applying a new tread rubber strip, which normallyhas been partially vulcanized, over the "cushion", and then, prior tointroducing the assembly into a curing chamber where vulcanization ofthe tread rubber is completed and the tread rubber is vulcanized to thetire carcass, the tire carcass unit is placed upon a retreading "rim"which is annular in form, generally like the periphery of the wheel thetire is mounted on during normal use, but is conventionally made up oftwo axially-adjacent sections which interlock with each other uponrotation of one section relatively to the other. To effect thisoperation, a tube or "bladder" for the reception of air or other fluidis positioned in the tire carcass and then the tire carcass ispositioned on one section of the rim, with the valve stem forintroduction of the fluid extending through a slot formed in the rimsection. Thereupon, the other section of the rim is placed in positionand the two sections are interlocked by circumferentially rotating thesecond section relatively to the other. However, the slot is wider thanthe thickness of the valve/or inlet stem and, when the two sections ofthe rim are being interlocked and the two are rotated circumferentiallyrelatively to one another, the tube has not yet been inflated and thevalve stem may become twisted and/or severly bent relatively to thebladder and it may break off or tear away from the bladder or develop aleak at its juncture with the bladder. This is a problem which has beeneffectively attacked in my co-pending application Ser. No. 942,878,filed Dec. 17, 1986, but there is a continuing search for otherapproaches to the solution of this serious problem in the retreadingfield.

It is accordingly an object of the present invention to provide animproved construction cooperating with the valve stem of a tube orbladder used for tire retreading which prevents apparatus.

It is another object of the invention to provide a retreading assemblywherein the tube or bladder used for retreading cooperates with its rimin such manner that its stem is prevented from damaging movements whenthe apparatus is assembled.

BRIEF SUMMARY OF THE INVENTION

These and other objects of the invention are achieved by a tireretreading bladder construction wherein the retreading tube is formedwith a valve stem which is threaded at its base, i.e., from the point itemerges from the tube body to at least 1.5 times the distance it extendsthrough the body of the retreading rim after it has been installed,e.g., at least about 1/2 in., preferably at least about 3/4 in., and aspecially-constructed spacing element is internally threaded tocooperate with the valve stem threads and surrounds the lower portion ofthe valve stem adjacent its point of connection to the tube. Thisspacing element enters and fills the slot in the rim when the tirecarcass to be retreaded is mounted for retreading, with the tube insideit, and the two sections of the rim are interlocked, and the spacingelement has flanges which overlie the radially inner and outer walls ofthe retreading rim. As a result of this cooperation between the spacingelement and the retreading rim, the stem does not bend or become exposedto damage and remains firmly in its desired position at all times.

BRIEF DESCRIPTION OF THE DRAWINGS

An illustrative embodiment of the invention is shown in the accompanyingdrawings wherein:

FIG. 1 is an exploded perspective view of the valve stem, and spacingelement and associated tube construction embodying feature of thepresent invention;

FIG. 2 is a fragmentary perspective view similar to FIG. 1 of anassembled retreading rim, showing the relationship of the two rimsections with the valve stem and spacing element embodying features ofthe present invention; and

FIG. 3 is a side elevation, partly in section, of the valve stem andspacer relationship shown in FIG. 2.

DETAILED DESCRIPTIN OF THE PREFERRED EMBODIMENT

Referring to the drawings, and particularly to FIG. 2, the retreadingrim is a substantially annular member 10 which is splitcircumferentially, i.e. formed from two axially-adjacent sections 12 and14. For ease of description, the split retreading rim 10 is shownwithout other appendages normally carried by a conventional retreadingrim but not relating to the present invention. The showing of the tirecarcass, which would normally surround the tube illustrated has alsobeen omitted. The section 12 shown in FIG. 2 has a plurality of catches16 around its inner surface. The second rim section 14, which cooperateswith rim section 12, has locking members or hooks 18 which are carriedby section 14 in spaced relationship corresponding to the catches 16.When the two rim sections are interlocked by relative circumferentialrotation to form the completed ring, as seen in FIG. 2, the lockingmembers 18 engage catches 16 to hold the two sections together in asecure fashion. Rim section 12 is also formed with a slot or cutout 20,as seen in FIG. 2. Mounted upon rim 10 is a retreading tube or bladder25 which is provided with a metal valve or inlet stem 28 which extendsthrough slot 20. The valve stem 28 is suitably anchored in the tube bodyin conventional manner, e.g. by having a flared or flanged inner endembedded in the tube rubber (not shown).

The valve stem 28 is threaded at its inner end 29, i.e., the endadjacent the elastomeric body of tube 25, as seen in FIG. 1, thethreading extending along the stem for at least 1/2 in., preferablyabout 3/4 in., but it can extend any desired additional distance, e.g.,the entire length of the stem, if desired. In the embodimentillustrated, the inner end 29 of the valve stem 28 which is threaded isalso slightly enlarged so that the stem 28 has an increased externaldiameter in this area 29 which is joined to the remainder of the stembody by a shoulder 30, and this is preferred, but the stem can be ofuniform external diameter, if desired. The free end of the valve stem 28is preferably threaded, as shown at 31, for reception of a cap (notshown), but this may be omitted, if desired.

In any case, in accordance with the invention, there is provided a rigidspacer element 35, suitably formed from metal. The spacer element 35 canbe viewed as an extension of the tube 28, in effect. As seen in FIGS. 1and 3, the spacer element 35 is generally cylindrical in shape with abody 36 and has a threaded axial bore 37. The body 36 has an innerflange 38 which is constructed to lie against the body of tube 28 andagainst the radially-outer wall of rim section 12, and an outer flange40 which will lie interiorly of the retreading rim against theradially-inner wall of rim section 12. The distance between the twoflanges 38 and 40 corresponds approximately to the thickness of theretreading rim which, in the usual case, is approximately 1/4 in., whichmay of course vary from rim to rim for which the spacing element 35 isconstructed.

The flanges 38 and 40 themselves can vary in thickness as long as theyare thick enough to be rigid and have strength to resist bendingstresses. The inner flange 38 which overlies the body of the tube 25should be relatively thin, e.g., approximately 1/16 in. in thickness sothat it will permit the tube to lie close to the retreading rim, and theouter edge of flange 38 may be beveled, if desired, as shown at 42 inFIG. 4, to facilitate its cooperation with the tube 28. The outer flange40 which lies interiorly of the retreading rim is preferably thickerthan flange 38 in order to facilitate hand manipulation of the spacerelement 35.

In the use of the construction of the invention, the rim section 12 isplaced upon a suitable supporting surface such as the floor. After thetire carcass has been prepared for retreading, e.g., by abrading theroad-engaging portion of the carcass, wrapping an uncured rubber cushionaround it, applying adhesive, and then applying a new, partially curedor vulcanized tread rubber strip, the tube 25 is placed in a deflatedcondition in the tire carcass to be retreaded and the spacer unit 35 isthreaded into place upon the valve stem 28 so that the spacer unit 35lies snugly against the tube 25. The advantage of having the threadedarea 29 of increased diameter is that the spacer element 35 can beslipped over the remainder of valve stem 28 of lesser diameter and needsto engage only the relatively short threaded portion 29. The carcass canalso be prepared for conventional retreading in any other conventionalmanner using partially-cured or uncured tread rubber. This priorpreparation of the carcass forms no part of the present invention and isdiscussed merely for illustrative purpose. The prepared carcass and thetube 25 are then placed over the rim section 12 with the valve stem 28of the tube 25 extending through the slot 20 and the spacer element 35being seated in the slot with the flanges 38 and 40 overlying theadjacent faces of the retreading rim, as seen in FIG. 2. Alternatively,the spacer element 35 can be loosely threaded upon the valve stem 28and, when the carcass and tube are mounted upon rim section 12 and thespacer element 35 is positioned in the slot 20 of rim section 12, thespacer element 35 can be tightened to draw the tube against the rimsection 12 so that a firm mounting results with the valve stem beingsecured against movement relatively to the tube 25 while at the sametime being centered in the slot 30 and being protected against damage byundesired contact with the surfaces of the rim section. Thereupon, thesecond rim section 14 is placed upon the first rim section 12 with thehooks 18 out of engagement with the catches 16 and, in the embodimentillustrated, it is rotated clock-wise so that the hooks engage thecatches and the two rim sections are interlocked for further handling,as seen in FIG. 2. The entire assembly is then ready to be placed in acuring apparatus (not shown) in conventional manner. As mentioned, thespacer element 35 can be viewed as an extension of the tube 25 whichextends into the slot 20 of retreading rim 12 to substantially fill theslot space circumferentially and protect the valve stem 28 and the tube25 from damage when the rim sections 12 and 14 are rotated relatively toone another.

After the vulcanization has been completed and the parts have cooled,rim section 14 is disengaged from the rim section 12, e.g. bycounter-clockwise rotation, and the carcass, retreaded tire, and thecontained retreading tube with attached spacer element 35 are removed,the tube and spacer element 35 then being also removed from the tire forre-use in another retreading operation. By reason of the construction ofthe invention, the tube can be used repeatedly without damage resultingfrom normal handling and interlocking of the rim sections.

It will be obvious that various changes and modifications can be madewithout departing from the scope of the invention as defined in theappended claims and it is intended, therefore, that all matter containedin the foregoing description and in the drawing shall be interpreted asillustrative only and not in any way as limitative of the invention.

We claim:
 1. In combination with a tire retreading rim formed from apair of axially-adjacent rim sections, one of which has a cutout forreceipt of the valve stem of a retreading tube mounted upon said rim, aretreading tube encircling said rim, said retreading tube having a valvestem extending therefrom and said tube having an extension of generallycylindrical form through which said stem extends, whereby the extensionsurrounds the portion of the stem adjacent said tube, said stem beingthreaded adjacent said tube and said extension being threadedly engagedwith said stem adjacent said tube, said extension being disposed in saidcutout with the valve stem extending inwardly of said rim said extensionsubstantially filling said cutout and to said rim section.
 2. For usewith a tire retreading rim formed from a pair of axially-adjacent rimsections one of which has a cutout for reception of the valve stem of aretreading tube mounted upon said rim, a retreading tube for encirclingsaid rim, said retreading tube having a valve stem extending therefrom,said stem being threaded adjacent said tube, and an internally-threadedspacer element of generally cylindrical form through which said stemextends and threadedly engaged therewith, whereby the spacer elementsurrounds the portion of the stem adjacent said tube, said spacerelement being shaped to be received in said cutout with the valve stemextending inwardly of said rim.
 3. A construction as defined in claim 2,wherein said spacer element has a cylindrical body portion for receptionin said cutout, and flanges at its ends to overlie the adjacent surfacesof the retreading rim section with which said spacer element isassociated.
 4. A construction as defined in claim 3, wherein the portionof said stem which is threaded has a greater diameter than the remainderof said stem.
 5. A retreading tube assembly for mounting on a retreadingrim formed from a pair of axially-adjacent rim sections, one of whichhas an axial cutout, a retreading tube, a valve stem extending from saidtube and being threaded adjacent said tube, and a spacer elementthreadedly engaged with said valve stem, said spacer element beingsubstantially cylindrical and having a body dimensioned to be receivedin said cutout and to substantially fill said cutout at leastcircumferentially, an inner flange overlying said tube and surroundingsaid valve stem, and an outer flange constructed to overlie the innerface of said rim section adjacent said cutout.
 6. An assembly as definedin claim 5, wherein said threaded portion of said valve stem adjacentsaid tube has a greater diameter than the remainder of said stem.